1. Field
The disclosure relates to oilfield downhole operations. More particularly, the disclosure relates to a self-lubricating swage device for expanding a tubular in a wellbore.
2. Prior Art
As is well known to those of skill in the art, expandable tubulars such as reformable deformed junctions have been known to the oilfield art. One will recognize the benefit of the exemplary deformed junction in that the junction is easily transported through the casing of a cased wellbore or through an open hole wellbore to its final destination at a junction between a primary and lateral borehole. Once the junction is properly positioned it is reformed into a Y-shaped junction to assist in completing the wellbore. In the fully reformed condition of the junction, the outer dimensions are generally greater than the ID of the casing or open hole. Thus of course it would be rather difficult to install the junction in its undeformed condition. Many methods have been used to expand tubulars or reform a deformed junction in the borehole. One of the prior art methods has been to employ a swaging device. Swaging devices generally comprise a conical or frustoconical hardened member having an outside diameter (OD) as large as possible while being passable through the wellbore casing or the open hole. This swage is urged to travel through a tubular or previously positioned deformed junction whereby the tubular or junction is reformed into an operational position. Where the tubular or junction is located in a vertical or near vertical wellbore, setdown weight alone often is sufficient to generate the approximately 100,000 pounds of force required to expand the tubular or reform the junction. Where the tubular or deformed junction is being placed in a highly deviated wellbore or a horizontal wellbore however, setdown weight might not be sufficient to force the swage device through the junction. In this event, one of skill in the art will recognize the hydraulic procedure alternative to setdown weight which includes an expansion joint located above the swage device, a drill tube anchor located above the expansion joint and a ball seat located below the expansion joint such that by dropping a ball, pressure can be applied to the tubing string whereby the expansion joint is forced to expand downhole which urges the swage device through the tubular or junction. Expansion joints are well known in the art, as are anchors and ball seats.
One of the problems encountered in swaging any tubular in a wellbore is the high frictional resistance that results from the contact between the swage and the contacted surface. Oftentimes the cross-sectional shape of the pipe is elliptical and not round. Swaging such a cross-sectional shape generates extremely high contact forces, which can cause galling and tearing of either or both of the swage and the pipe, which can in turn increase the force required to push the swage through the tubular.
Traditional methods of reducing friction include the use of conventional lubricants. In the application at hand, the use of conventional lubricants is limited because the lubricant must be applied to the surfaces immediately before the swage contacts the junction or the pipe. The biggest drawback to this type of application is the cost of placing the lubricant into a position where it can be utilized. Furthermore, since conventional lubricants typically have an adverse effect on cement used in the vicinity within the wellbore, such lubricants must be removed from the area before the cementing operation is commenced. There is a high cost associated with removing the lubricant prior to the application of the cement. Although a multitude of downhole lubricants and friction reducers are commercially available, hole depths and pipe configurations almost always render their use uneconomical.
Similar drawbacks are experienced during the removal of the prior art swaging devices. The obstacles encountered with respect to lubrication to force the swaging devices into a wellbore are the same as the obstacles encountered in the removal of the swaging devices from the wellbore. The metal (or other material) of the tubulars being expanded generally has a certain amount of resilience such that after the swage device has been forced through the tubular to expand it, the tubular itself will rebound to a smaller ID than the OD of the swage device by several thousandths of an inch. Because of the rebound, nearly as much lifting force is required on the swage device to remove it from the wellbore as is needed to initially urge the swage through the tubular. In the absence of any type of lubrication, this lifting force can be as much as 100,000 pounds. Although a drilling rig can easily pull ten times this weight, in a highly deviated or horizontal wellbore, the friction created on the curvature of the well can be high enough to absorb all of the force imparted at the surface and leave none available for the swage. Thus the tool is stuck. The amount of force necessary to pull the swage through the newly expanded and unlubricated tubular can also be sufficient to damage other well tools or tubulars. Such damage can of course cost significant sums of money to repair and require significant time both to diagnose and to repair.
The self-lubricating swage avoids the above drawbacks by creating a self-lubricating single or two-part swage device. The single part device comprises a lubricious material associated with the swage. The two-part device comprises a primary swaging tool and second expansion device positioned ahead of the primary swaging tool for expanding a tubular in a wellbore. For simplicity, the second expansion device is termed a xe2x80x9cnose swagexe2x80x9d. It will be understood that this term is not known to the applicants hereof to have any specific meaning in the art and is selected for use only to describe what is taught herein and the equivalents thereof. The self-lubricating nose swage can be utilized with any type of primary swaging tool. The primary swaging tool is supported on a mandrel, and the nose swage member is supported on an end of the mandrel. The nose swage member may be fabricated of a first lubricious solid material, which is preferably a smearable material such as bronze. Alternatively, the nose swage may be constructed primarily of a different first material and coated with a layer of lubricious material. Additionally or alternatively, the nose swage may contain a plurality of grooves disposed therein, which may be filled with a second lubricious material such as polytetrafluoroethylene. The self-lubricating swage device of the present invention is employable in place of a conventional swage, the function of which being fully assimilated.